I've seen these types, glued to their phones likes its life or death!

But there are two things you can do about it: One is too stare at them intently till you get their attention, when you do LAUGH at them and walk away! They'll ponder that for hours!
And two: If its during a movie or the above mentioned concert (Those ladies can really belt it out by the way!) go over and pull it out if their little paws, what follows will either be the classic "deer in the headlights" look or something that will remind you of a cat clawing for its life, then say loudly "TIME OUT!!!" They'll sit there or go into babble mode and as you watch they'll either go into withdraw, the fetal position, or a severe case of the DTs, all the while either screaming for their phone back or threating you with their stylus! Oh it's great fun!!

Dale